Z Chamber 10 Developer Commentary
This was chamber 08 in PortalZ: The First Slice and chamber 12 (and chamber 17 in the code) in PortalZ: The 2020 Slice.
Developer commentary may include spoilers; I recommend you finish PortalZ before reading further.
I knew I wanted to do a companion cube level, and I really liked the idea of making the player guide the cube through the level without killing it. After Portal 2 came out, I realized I had inadvertently been following primitive versions of some patterns that were more fleshed out in co-op levels.
Also, fun fact, I worked on some of the earliest iterations of this level before I learned to make a cube dropper drop multiple cubes since it only ever needed to drop one companion cube.
There was no reason the escape hatch had to be this dramatic; it was just too much fun to not do it once, and a part of a level that was all about cubes on top of cubes on top of cubes seemed the best place for it.
One additional note: This was chamber 17 for the longest time, just to have it be the same number as Portal's companion cube chamber, but it makes much more sense between chamber 09 and chamber 11 (which was previously chamber 10) so you play it while countering turrets with a cube is fresh in your mind, and manipulating the cube from a distance with portals is good preparation for the cube fling in chamber 11.